Subterranean hydrocarbon-containing formations penetrated by well bores are often treated with aqueous acid compositions to stimulate the production of hydrocarbons therefrom. For instance, “acidizing” introduces an aqueous acid composition into a subterranean formation under pressure so that the acid composition flows through the pore spaces of the formation. The acid composition reacts with acid soluble materials contained in the formation thereby increasing the size of the pore spaces and the permeability of the formation. Another example is “fracture-acidizing,” which promotes the creation of one or more fractures in the formation and introduces an aqueous acid composition into the fractures to etch the fracture faces whereby flow channels are formed when the fractures close. The aqueous acid composition also enlarges the pore spaces in the fracture faces and in the formation.
Acidizing and fracture-acidizing well stimulation treatments have been performed successfully over the years, but these processes illustrate a problem that typically accompanies acid-related operations: they are accompanied by acid-promoted corrosion of metal pumps, tubular goods and other equipment that introduce the aqueous acid compositions into the subterranean formation to be treated. The expense associated with repairing or replacing corrosion damaged tubular goods and equipment can be very high. The corrosion rate of metal equipment and tubular goods moreover is increased by elevated temperatures that are encountered in deep formations, and the corrosion process results in at least a partial neutralization of the aqueous acid compositions before they can react with acid-soluble materials in the formations.
Other industrial applications employ aqueous acid compositions that contact and react with acid soluble materials. In such applications, metal equipment and metal surfaces also contact the acid compositions, and the resulting corrosion of such metal equipment and surfaces is highly undesirable.